The manufacture of a semiconductor device, a liquid crystal device, or the like requires forming a thin film on a work piece such as a semiconductor wafer or a glass substrate, and performing sputtering, etching, and other similar types of treatment on the work piece. In these types of treatment, the temperature of the work piece determines the film forming rate, the etching rate, and the like, thereby affecting the quality of the resultant thin film or the like significantly. For that reason, the forming of a thin film or other similar types of treatment is performed with the use of a unitary work heating device as in, for example, Patent Literature 1, where a attraction electrode for causing a work piece to stick by attraction and a resistance heating element are built in a ceramic or similar plate main body of the work heating device, and the heating element is energized and heated so that the stuck work piece reaches a desired temperature.
In such unitary work heating devices, it has been a common practice to manufacture the plate main body having the built-in attraction electrode and heating element by printing a given pattern on a ceramic green sheet in conductive ink having, as a main component, a high melting point metal such as tungsten, layering the ceramic green sheet and another ceramic green sheet, and sintering the layers simultaneously. However, in unitary work heating devices where components, including ceramic green sheets on which conductive ink is used for printing, are sintered at once, it is difficult to achieve uniformity in heating temperature throughout the entire surface of a work piece due to an error in the thickness of the heating element, an error in the distance from the heating element to the work piece, and the like. Patent Literature 2, for example, has therefore proposed a layered-structured work heating device in which a heating element is sandwiched between a attraction electrode-containing ceramic substrate which is sintered unitarily with a attraction electrode contained therein and a separately sintered ceramic substrate, and the two ceramic substrates are bonded with an adhesive.
Further, in recent years, along with the increase in the size of a semiconductor wafer, a glass substrate, and the like, it is increasingly important to maintain the temperature of a work piece uniformly with high precision. Ways to transmit heat uniformly have therefore been devised for layered-structured work heating devices as illustrated in FIG. 4, where a soaking plate 31 made from an aluminum plate or the like is interposed between a chuck member 1, which includes a attraction electrode 3 for work attraction, and heater member 5, which includes a heating element 7, so that heat from the heating element 7 is transmitted uniformly to the entire surface of a work piece 18.
However, the distance from the heating element 7 of the heater member to the work piece 18 is large in the structure that interposes the soaking plate 31 between the chuck member 1 and the heater member 5 because an adhesive layer 32 for layering these is included in the distance as well. Heat transmission to the work piece consequently takes that much longer time, and more different types of materials result in complicated work temperature control and difficulty in carrying out fine temperature control which affects the quality of a thin film or the like. On the other hand, the chuck member of a conventional layered-structured work heating device can be warped or bent, or even cracked in some cases, when the work heating device is in use for a long duration, which means that the lifespan of the chuck member determines the product lifespan of the work heating device itself.